Parameterization of stromatoporoid shape

Abstract

Stromatoporoid cross-sectional shape can be considered as a product of the interaction of three morphological variables: the relative proportions of basal, vertical and diagonal dimensions. The gross arrangement of internal lamination can be superimposed upon the resulting outlines. These shapes are taken to represent cross sections in any vertical plane through the centre of the coenosteum. This simple parameterization scheme is presented in triangular arrays which include the stromatoporoid morphotypes laminar, domical and bulbous, and varieties of them together with forms not utilized by stromatoporoids. Dendroid and irregular forms are too complex to be readily included in the scheme.Smooth and ragged varieties of laminar and domical forms are distinguished and related to sedimentation on the flanks of the coenosteum. Two types of mutual arrangement of latilaminae within the coenosteum are recognized: enveloping, where they completely overlap previous latilaminae, and non-enveloping, where they do not. Laminar4omical-bulbous forms represent a series generated mainly by reduction of the basal dimension. They commonly exhibit enveloping latilaminae except in ragged varieties and some extended domes. Measurement of defined dimensions in the field allows stromatoporoid morphotypes to be plotted onto the triangular arrays and provides a rapid method of displaying the range of forms present.The stromatoporoid skeleton commonly has a concavoxonvex appearance with a flattened concave base and a convex upward upper surface 16-Lethaia 3/78

Treatise Online, no. 25: Part E, Revised, Volume 4, Chapter 9B: External morphology of the Paleozoic Stromatoporoidea: Shapes and growth habits

“…2). The high domical subgroup here combines the previously separated high and extended domical categories of KerShaW and riDiNg (1978) and KerShaW (1990KerShaW ( , 1998, and the separated high, extended and highly extended subdivisons of luczyNSKi (2005). luczyNSKi also proposed low and high subgroups for the bulbous category.…”

“…Many workers have attempted to establish an acceptable terminology for classifying the chief skeletal shapes (e.g., NoBle, 1970;aBBott, 1973;KerShaW & riDiNg, 1978, 1980StearN, 1983StearN, , 1984KerShaW, 1998), singling out a comparatively small number of major groups of forms. The scheme recognized by KerShaW (1998) included the terms: laminar, tabular, domical, columnar, bulbous, dendroid, expanding-conical, digitate, and irregular.…”

“…There are only a few localities, like Gotland, where oriented, uniquely well-preserved material can be sampled, sectioned, and measured (see KerShaW & riDiNg, 1978;KerShaW, 1984). To be useful, whole specimens must be cut longitudinally along the growth axis, and this is seldom possible in more typical field occurrences.…”

Recent studies on the Silurian of the western part of Ukraine

“…Kershaw 1981Kershaw , 1990Kershaw , 1998Łuczyński 1998, 2003, 2009). For detailed description of the parameterization method see Kershaw and Riding (1978) and Łuczyński (2005).…”

Treatise Online, no. 31: Part E, Revised, Volume 4, Chapter 13: Paleoecology of the Paleozoic Stromatoporoidea

“…Stromatoporoid early growth often formed sheetlike skeletons across the substrate, and subsequent growth was concentrated in central areas, producing a smooth, nonenveloping profile (KerShaw & riding, 1978); uncommonly, others are fully enveloping (see webby & KerShaw, 2011, p. 7). The resulting basal surfaces of skeletons display concentric ridges where successive overlapping layers touch the substrate, enhanced into minor ragged edges, which may be due to a little sedimentary material collected on the edges as successive layers grew.…”